The present invention relates to aircraft and more specifically to aircraft with a strut-braced foldable wing, and to methods of folding the wing on such an aircraft.
There is a trend towards increasingly fuel efficient passenger aircraft, for which it is desirable to have correspondingly large wing spans. However, the maximum aircraft span is often effectively limited by airport operating rules which govern various clearances required when manoeuvring around the airport (such as the span and/or ground clearance required for gate entry and safe taxiway usage).
In some suggested designs, aircraft are provided with wings which may be folded upwardly to reduce the span of the aircraft on the ground (compared to when the aircraft is configured for flight). However, a disadvantage with such arrangements is that they tend to be unduly heavy. For example, they may require high capacity (and therefore heavy) actuators to fold the wing. Alternatively or additionally, the wing structure near the folding joint may need to be significantly reinforced in order to withstand and transfer the wing loading across the joint.
Another problem encountered on large wing span aircraft, is that the magnitude of the bending moments generated at the wing root tend to be correspondingly large. The structure at the wing root must be sufficiently strong to withstand these large bending moments, which can lead to an undesirable weight increase in the aircraft.
To address this problem, it is known to provide aircraft with strut-braced wings in which a strut structure transfers wing loadings in the outer region of the wing, away from the inner region of the wing (and thus away from the wing root). Such an arrangement does not require the wing root structure to be as strong and can lead to a weight saving, which in some cases can be sufficient to offset the weight and/or drag penalties associated with the strut structure, especially for very large wingspan aircraft.